This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPPthird generation partnership projectACKacknowledgeBTSbase transceiver systemBWbandwidthC-Planecontrol planeCCcomponent carrierCNcore networkCQIchannel quality indicatorDCdual carrierDLdownlink (eNB, Node B towards UE)DTXdiscontinuous transmissionE-DCHenhanced downlink channelEDGEenhanced data rates for GSM evolutioneNBEUTRAN Node B (evolved Node B)EPCevolved packet coreEUTRANevolved UTRAN (LTE)GGSNgateway general packet radio system support nodeGSMglobal system for mobile communicationHARQhybrid automatic repeat requestHOhandoverH-RNTIHS-DSCH radio network transaction identifierHS-DSCHhigh speed downlink shared channelHS-SCCHhigh speed shared control channelHSPAhigh speed packet accessHSDPAhigh speed downlink packet accessHSUPAhigh speed uplink packet accessI-HSPAinternet HSPA (evolved HSPA)IPinternet protocolL1layer 1 (physical (Phy) layer)L2layer 2 (MAC layer)LTElong term evolutionMACmedium access controlMM/MMEmobility management/mobility management entityNACKnot acknowledge/negative acknowledgeNBAPNode B application part (signaling)Node Bbase station (includes BTS)OFDMAorthogonal frequency division multiple accessO&Moperations and maintenancePDCPpacket data convergence protocolPDUprotocol data unitPhyphysicalPMIpre-coding matrix indexPRBphysical resource blockPDCCHphysical downlink control channelPDSCHphysical downlink shared channelPUCCHphysical uplink control channelPUSCHphysical uplink shared channelRACHrandom access channelRATradio access technologyRBradio bearerREresource elementRLCradio link controlRNCradio network controllerRNTIradio network temporary identifierROHCrobust (internet) header compressionRRCradio resource controlSAWstop-and-waitSC-FDMAsingle carrier, frequency division multiple accessSGSNserving gateway support nodeSGWserving gatewaySINRsignal to interference plus noise ratioSRscheduling requestTCPtransmission control protocolTFRCTCP-friendly rate controlTTItransmit time intervalU-Planeuser planeUEuser equipmentULuplink (UE towards eNB, Node B)UTRANuniversal terrestrial radio access networkWCDMAwideband code division multiple access
The specification of a communication system known as evolved UTRAN (EUTRAN, also referred to as UTRAN-LTE or as EUTRA) has been specified by 3GPP in Rel-8 (release eight). As specified, the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.10.0 (2009-9), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (EUTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8). This system may be referred to for convenience as LTE Rel-8 (which also contains 3G HSPA and its improvements). In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3GPP TS 36.300, V9.1.0 (2009-9).
FIG. 1A reproduces FIG. 4.1 of 3GPP TS 36.300, and shows the overall architecture of the E-UTRAN system. The E-UTRAN system includes eNBs, providing the EUTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1 MME interface and to a Serving Gateway (SGW) by means of a S1 interface. The S1 interface supports a many to many relationship between MMEs/Serving Gateways and eNBs.
The eNB hosts the following functions:
functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);
IP header compression and encryption of the user data stream;
selection of a MME at UE attachment;
routing of User Plane data towards Serving Gateway;
scheduling and transmission of paging messages (originated from the MME);
scheduling and transmission of broadcast information (originated from the MME or O&M);
scheduling and transmission/reception of user data over the radio interface; and
measurement and measurement reporting configurations to provide mobility and scheduling.
Of particular interest herein are the further releases of 3GPP LTE targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A).
Reference can be made to 3GPP TR 36.814, V1.3.1 (2009-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Further Advancements for E-UTRA Physical Layer Aspects (Release 9). Reference can also be made to 3GPP TR 36.913, V8.0.1 (2009-3), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E-UTRA (LTE-Advanced) (Release 8). A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost.
GSM, WCDMA, and LTE in their first releases utilized single carrier transmission. Since then, multicarrier operation has been introduced in GERAN EGDE and WCDMA HSDPA (TS25.308 Rel-8-Rel-9) and HSUPA in (TS25.319 Rel9) operation. In HSPA multicarrier operation, the UE and Node B transmit on two parallel carriers in quite an independent manner and the multicarrier operation can be seen as multiple parallel single carrier transmissions performed on different carrier frequencies to/from the single UE. The multicarrier operation in HSDPA (dual cell or dual band) supports only single carrier uplink operation, but the Dual carrier HSUPA requires dual carrier downlink operation.
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of Rel-8 LTE, e.g., up to 100 MHz, to achieve the peak data rate of 100 mega-bits per second (Mbit/s) for high mobility and 1 Gbit/s for low mobility. LTE-A (to be included into 3GPP Release-10) is going to include carrier aggregation (CA), providing the capability to aggregate together up to five LTE carriers referred to as Component Carriers (CCs). The basic principle of CA in LTE for a single RAT is presented on FIG. 1B, which shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form MxRel-8 BW, e.g. 5×20 MHz=100 MHz given M=5.
Rel-8 terminals receive/transmit on one component carrier, whereas LTE-Advanced terminals may receive/transmit on multiple component carriers simultaneously (as shown in FIG. 1B) to achieve higher (e.g., wider) bandwidths. Basic scenarios for both downlink and uplink will be included into Release-10 (Rel-10). Similar work has also been carried out in the 3GPP in the context of HSDPA. In Release-10 the work on four-carrier HSDPA is currently ongoing, providing support for up to four, five mega-Hertz (MHz) carriers.
In LTE, the carrier aggregation, also called the multicarrier solution, is one of the main features to be defined for Rel-10 (TR36.814 and TR36.912) for LTE-A. In LTE also the basic principles are similar as the component carriers (single Rel-8 carrier) operate independently. Also in this specification, work will contain the operation with single carrier uplink with multiple downlink carriers.
While carrier aggregation is beneficial, especially because of the large amount of bandwidth it provides, integration is still a problem.